Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
  • C08G18/72—Polyisocyanates or polyisothiocyanates
  • C08G18/74—Polyisocyanates or polyisothiocyanates cyclic
  • C08G18/76—Polyisocyanates or polyisothiocyanates cyclic aromatic
  • C08G18/7657—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings
  • C08G18/7664—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings containing alkylene polyphenyl groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/08—Processes
  • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/08—Processes
  • C08G18/09—Processes comprising oligomerisation of isocyanates or isothiocyanates involving reaction of a part of the isocyanate or isothiocyanate groups with each other in the reaction mixture
  • C08G18/092—Processes comprising oligomerisation of isocyanates or isothiocyanates involving reaction of a part of the isocyanate or isothiocyanate groups with each other in the reaction mixture oligomerisation to isocyanurate groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/08—Processes
  • C08G18/16—Catalysts
  • C08G18/18—Catalysts containing secondary or tertiary amines or salts thereof
  • C08G18/20—Heterocyclic amines; Salts thereof
  • C08G18/2009—Heterocyclic amines; Salts thereof containing one heterocyclic ring
  • C08G18/2036—Heterocyclic amines; Salts thereof containing one heterocyclic ring having at least three nitrogen atoms in the ring
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/30—Low-molecular-weight compounds
  • C08G18/32—Polyhydroxy compounds; Polyamines; Hydroxyamines
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/30—Low-molecular-weight compounds
  • C08G18/32—Polyhydroxy compounds; Polyamines; Hydroxyamines
  • C08G18/3225—Polyamines
  • C08G18/3237—Polyamines aromatic
  • C08G18/3243—Polyamines aromatic containing two or more aromatic rings
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
  • C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
  • C08J3/075—Macromolecular gels
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K7/00—Use of ingredients characterised by shape
  • C08K7/22—Expanded, porous or hollow particles
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G2101/00—Manufacture of cellular products
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G2110/00—Foam properties
  • C08G2110/0091—Aerogels; Xerogels
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G2115/00—Oligomerisation
  • C08G2115/02—Oligomerisation to isocyanurate groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G2330/00—Thermal insulation material
  • C08G2330/50—Evacuated open-celled polymer material

Definitions

• the present invention relates to a process for the preparation of porous materials in the form of aerogels or xerogels comprising reacting at least one polyfunctional isocyanate with an amine component comprising at least one polyfunctional substituted aromatic amine in the presence of a solvent and a catalyst, wherein the reaction is carried out in the absence of water.
• the invention relates to the aerogels and xerogels thus obtainable as well as the use of aerogels and xerogels as insulating material and in vacuum insulation panels.
• Porous materials for example polymer foams, with pores in the size range of a few micrometers or significantly lower and a high porosity of at least 70% are due to theoretical considerations particularly good heat insulators.
• Such porous materials with a small average pore diameter may be present, for example, as organic xerogels.
• xerogel is not consistently used consistently.
• a xerogel is understood to mean a porous material prepared by a sol-gel process wherein the liquid phase is removed from the gel by drying below the critical temperature and below the critical pressure of the liquid phase ("subcritical conditions")
• aerogels are generally said to be when the removal of the liquid phase from the gel has been carried out under supercritical conditions
• a sol is first prepared based on a reactive organic gel precursor and then the sol is replaced with a sol
• the liquid In order to obtain a porous material, for example a xerogel, from the gel, the liquid must be removed, this step being referred to below as drying.
• WO-95/02009 discloses isocyanate-based xerogels which are particularly suitable for applications in the field of vacuum insulation.
• the publication also discloses a sol-gel-based process for the preparation of xerogels, known, including aromatic polyisocyanates and an unreactive solvent are used.
• Other compounds having active H atoms include aliphatic or aromatic polyamines or polyols.
• the examples disclosed in the publication include those in which a polyisocyanate is reacted with diaminodiethyltoluene.
• the disclosed xerogels generally have average pore sizes in the range of 50 ⁇ on. In one example, a mean pore diameter of 10 ⁇ is called.
• WO-2008/138978 discloses xerogels containing from 30 to 90% by weight of at least one polyfunctional isocyanate and from 10 to 70% by weight of at least one polyfunctional aromatic amine whose volume-weighted mean pore diameter is at most 5 micrometers.
• the unpublished EP-A 09178783.8 describes porous materials based on polyfunctional isocyanates and polyfunctional aromatic amines, wherein the amine component comprises polyfunctional substituted aromatic amines.
• the preparation of said porous materials is carried out by reacting isocyanates with the desired amount of amine in a solvent which is unreactive with respect to the isocyanates.
• the formation of the urea linkages takes place exclusively by reaction of the isocyanate groups with the amino groups used. The reaction is uncatalyzed.
• the material properties, in particular the mechanical stability and / or the compressive strength and the thermal conductivity, of the known porous materials based on polyurea are not sufficient for all applications.
• the underlying formulations show shrinkage during drying, reducing porosity and increasing density.
• the libration time, i. H. the time required to gel the starting compounds often too long.
• the average pore size of known low density porous materials is often too high. Especially at pressures above the vacuum range, z. B. in the range of 1 to 1000 mbar, a small average pore size in terms of favorable thermal conductivity of advantage.
• a particular problem with the known from the prior art formulations based on isocyanates and amines are so-called mixing errors.
• Mixing errors occur due to the high reaction rate between isocyanates and amino groups, since the gelation reaction is already well advanced before complete mixing. Mischmay lead to aerogels or xerogels with heterogeneous and insufficient material properties. A concept for reducing the phenomenon of mixing errors is thus generally desirable. Too long a gel time, d. H. too long a time to complete gelation of the gel precursor, but should be avoided.
• an airgel or xerogel should be provided which does not have the aforementioned disadvantages or to a lesser extent.
• the porous materials in the form of aerogels or xerogels should be compared to the prior art. have improved thermal conductivity in a vacuum.
• the aerogels and xerogels should also have a low thermal conductivity even at pressures above the vacuum range, in particular in a pressure range of approximately 1 mbar to approximately 100 mbar. This is desirable because pressure increases over time in vacuum panels.
• a further object of the present invention was to provide a porous material with a low heat conductivity in the aerated state, ie in the region of 1000 mbar.
• the airgel or xerogel should simultaneously have a high porosity, a low density and a sufficiently high mechanical stability.
• the process according to the invention for producing an airgel or xerogel comprises the reaction of the following components (a1) and (a2) in the absence of water, in the presence of a solvent and at least one catalyst:
• R 1 and R 2 may be the same or different and are independently selected from hydrogen and linear or branched alkyl groups having from 1 to 6 carbon atoms and wherein all substituents Q 1 to Q 5 and Q 1 'to Q 5 ' are the same or different and independently of one another are selected from hydrogen, a primary amino group and a linear or branched alkyl group having from 1 to 12 carbon atoms, wherein the alkyl group may carry further functional groups, provided that the compound according to the general formula I comprises at least two primary amino groups, wherein at least one of Q 1 , Q 3 and Q 5 is a primary amino group and at least one of Q 1 ', Q 3 ' and Q 5 'is a primary amino group and
• Q 2 , Q 4 , Q 2 'and Q 4 ' are chosen so that the compound according to the general formula I is at least one linear or branched alkyl group which can carry further functional groups, having from 1 to 12 carbon atoms in ⁇ - Having position to at least one primary amino group attached to the aromatic nucleus,
• polyfunctional aromatic amine (a2-u), which is different from the amines (a2-s) according to the general formula I, to form the aerogels or xerogels according to the invention.
• a2-u further polyfunctional aromatic amine
• component (a1) are referred to collectively below as component (a1).
• component (a2) are referred to collectively below as component (a2). It will be apparent to those skilled in the art that the said monomer components are present in reacted form in the porous material.
• functionality of a compound is to be understood as meaning the number of reactive groups per molecule.
• the functionality is the number of isocyanate groups per molecule.
• the functionality denotes the number of reactive amino groups per molecule.
• a multifunctional compound has a functionality of at least 2.
• a polyfunctional compound contains at least two of the abovementioned functional groups per molecule.
• the reaction proceeds in the absence of water.
• the skilled worker is aware that traces of water in the solvent can not be completely excluded. Small amounts of water do not affect the present invention. Accordingly, in the absence of water, it should be understood that the total amount of water based on the total weight of components (a1) and (a2) and water is below 0.1% by weight, in particular from 0 to 0.09% by weight, particularly preferably from 0 to 0.08% by weight .-%.
• Component (a1) is below 0.1% by weight, in particular from 0 to 0.09% by weight, particularly preferably from 0 to 0.08% by weight .-%.
• At least one polyfunctional isocyanate is reacted as component (a1).
• the amount of component (a1) used is preferably from 20 to 80% by weight, in particular from 25 to 75% by weight, particularly preferably from 35 to 68% by weight, in each case based on the total weight the components (a1) and (a2) which gives 100% by weight.
• Suitable polyfunctional isocyanates are aromatic, aliphatic, cycloaliphatic and / or araliphatic isocyanates. Such polyfunctional isocyanates are known per se or can be prepared by methods known per se.
• polyfunctional isocyanates can also be used in particular as mixtures, so that component (a1) in this case contains various polyfunctional isocyanates.
• Suitable polyfunctional isocyanates suitable as monomer building blocks (a1) have two (referred to below as diisocyanates) or more than two isocyanate groups per molecule of the monomer component.
• 2,2'-, 2,4'- and / or 4,4'-diphenylmethane diisocyanate M DI
• 1, 5-naphthylene diisocyanate NDI
• 2,4- and / or 2,6-tolylene diisocyanate TDI
• 3,3'-dimethyldiphenyl diisocyanate 1, 2-diphenylethane diisocyanate and / or p-phenylene diisocyanate (PPDI)
• PPDI p-phenylene diisocyanate
• tri-, tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate 2- Methylpentamethylene-1,5-diisocyanate, 2-ethylbutylene-1,4-diisocyanate, penta-methylene-1,5-diisocyanate, butylene-1,4-diisocyanate, 1-is
• polyfunctional isocyanates (a1) aromatic isocyanates are preferred.
• the following embodiments are particularly preferred as polyfunctional isocyanates of component (a1): i) polyfunctional isocyanates based on tolylene diisocyanate (TDI), in particular 2,4-TDI or 2,6-TDI or mixtures of 2,4- and 2, 6-TDI;
• TDI tolylene diisocyanate
• polyfunctional isocyanates based on diphenylmethane diisocyanate in particular 2,2'-M DI or 2,4'-MDI or 4,4'-MDI or oligomeric MDI, the also referred to as Polyphenylpolymethylenisocyanat, or mixtures of two or three of the aforementioned Diphenylmethandiisocyanate, or crude MDI, which is obtained in the preparation of MDI, or mixtures of at least one oligomer of MDI and at least one of the aforementioned low molecular weight MDI derivatives;
• MDI diphenylmethane diisocyanate
• 2,2'-M DI or 2,4'-MDI or 4,4'-MDI or oligomeric MDI the also referred to as Polyphenylpolymethylenisocyanat, or mixtures of two or three of the aforementioned Diphenylmethandiisocyanate, or crude MDI, which is obtained in the preparation of MDI, or mixtures of at least one oli
• oligomeric diphenylmethane diisocyanate is one or a mixture of several oligomeric condensation products and thus derivatives of diphenylmethane diisocyanate (MDI).
• the polyfunctional isocyanates may preferably also be synthesized from mixtures of monomeric aromatic diisocyanates and oligomeric MDI.
• Oligomeric MDI contains one or more polynuclear condensation products of MDI having a functionality of more than 2, in particular 3 or 4 or 5. Oligomeric MDI is known and is often referred to as polyphenylpolymethylene isocyanate or else as polymeric MDI. Oligomeric MDI is usually composed of a mixture of MDI-based isocyanates with different functionality. Typically, oligomeric MDI is used in admixture with monomeric MDI.
• the (average) functionality of an isocyanate containing oligomeric MDI may vary in the range of about 2.2 to about 5, especially from 2.4 to 3.5, especially from 2.5 to 3.
• Such a mixture of MDI based multifunctional isocyanates with different functionalities is especially the crude MDI, which is obtained in the production of MDI.
• Polyfunctional isocyanates or mixtures of several polyfunctional isocyanates based on MDI are known and are sold, for example, by BASF Polyurethanes GmbH under the name Lupranat®.
• component (a1) is preferably at least two, in particular at least 2.2 and more preferably at least 2.5.
• the functionality of component (a1) is preferably from 2.2 to 4 and more preferably from 2.5 to 3.
• the content of isocyanate groups of component (a1) is preferably from 5 to 10 mmol / g, in particular from 6 to 9 mmol / g, particularly preferably from 7 to
• component (a1) consists of at least one polyfunctional isocyanate selected from diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-2,2'-diisocyanate and oligomeric diphenylmethane diisocyanate.
• component (a1) particularly preferably contains oligomeric diphenylmethane diisocyanate and has a functionality of at least 2.5.
• the viscosity of the component (a1) used can vary within a wide range.
• the component (a1) preferably has a viscosity of 100 to 3000 mPa.s, particularly preferably of 200 to 2500 mPa.s.
• component (a2) in the context of component (a2) at least one Contrexio- nelles substituted aromatic amine (a2-s) according to the general formula I.
• R 1 and R 2 may be the same or different and are independently selected from hydrogen and linear or branched alkyl groups having 1 to 6 carbon atoms and wherein all substituents Q 1 to Q 5 and Q 1 'to Q 5 ' are the same or different and are independently selected from hydrogen, a primary amino group and a linear or branched alkyl group having 1 to 12 carbon atoms, which alkyl group may carry further functional groups, provided that - the compound according to the general formula I at least two primary amino groups wherein at least one of Q 1 , Q 3 and Q 5 is a primary amino group and at least one of Q 1 ', Q 3 ' and Q 5 'is a primary amino group and
• Q 2 , Q 4 , Q 2 'and Q 4 ' are chosen so that the compound according to the general formula I with at least one linear or branched alkyl group, which may optionally carry further functional groups, with of from 1 to 12 carbon atoms in the ⁇ -position to at least one primary amino group bonded to the aromatic nucleus, and optionally at least one further polyfunctional aromatic amine (a2-u) other than the amines (a2-s) of the general formula I differentiates, implemented.
• Component (a2) thus consists of polyfunctional aromatic amines, wherein the polyfunctional aromatic amines (a2-s) according to the general formula I are an ingredient.
• Polyfunctional amines are to be understood as those which have at least two isocyanate-reactive amino groups per molecule.
• Primary and secondary amino groups are reactive toward isocyanates, the reactivity of the primary amino groups generally being significantly higher than that of the secondary ones.
• the amount of component (a2) used is preferably from 20 to 80% by weight, in particular from 25 to 75% by weight, particularly preferably from 32 to 65% by weight, in each case based on the total weight of components (a1) and (a2), which gives 100% by weight.
• R 1 and R 2 in the general formula I are the same or different and are independently selected from hydrogen, a primary amino group and a linear or branched alkyl group having from 1 to 6 carbon atoms.
• Q 2 , Q 4 , Q 2 'and Q 4 ' are selected so that the substituted aromatic see amine (a2-s) comprises at least two primary amino groups, each having one or two linear or branched alkyl groups having from 1 to 12 Have carbon atoms in the a-position, which can carry further functional groups. If one or more of Q 2 , Q 4 , Q 2 'and Q 4 ' are selected to correspond to linear or branched alkyl groups having from 1 to 12 carbon atoms bearing further functional groups, then amino groups and / or hydroxy groups and or halogen atoms are preferred as such functional groups.
• alkyl groups in the context of the substituents Q according to the general formula I are preferably selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl and tert-butyl.
• the amines (a2-s) are selected from the group consisting of 3,3 ', 5,5'-tetraalkyl-4,4'-diaminodiphenylmethane, 3,3', 5,5'-tetraalkyl-2,2 ' - Diaminodiphenylmethan and 3,3 ', 5,5'-tetraalkyl-2,4'-diaminodiphenylmethane, wherein the alkyl groups in 3, 3', 5 and 5 'position may be the same or different and are selected independently of each other from linear or branched alkyl groups having from 1 to 12 carbon atoms which may carry further functional groups.
• the aforementioned alkyl groups are methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl or t-butyl C unsubstituted).
• one, several or all of the hydrogen atoms of one or more alkyl groups of the substituents Q may be replaced by halogen atoms, in particular chlorine.
• one, several or all of the hydrogen atoms of one or more alkyl groups of the substituents Q may be replaced by N H2 or OH.
• the alkyl groups in the context of the general formula I are composed of carbon and hydrogen.
• component (a2) comprises 3, 3 ', 5,5'-tetraalkyl-4,4'-diaminodiphenylmethane, wherein the alkyl groups may be the same or different and are independently selected from linear or branched alkyl groups with From 1 to 12 carbon atoms which may optionally bear functional groups.
• the abovementioned alkyl groups are preferably selected from unsubstituted alkyl groups, in particular methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl and tert-butyl, particularly preferably from methyl and ethyl.
• polyfunctional amines of the type (a2-s) are known per se to the person skilled in the art or can be prepared by known methods.
• One of the known methods is the reaction of aniline or of derivatives of aniline with formaldehyde under acid catalysis, in particular the reaction of 2,4- or 2,6-dialkylaniline.
• component (a2) may also comprise other multifunctional aromatic amines (a2-u) which differ from the amines of structure (a2-s).
• the aromatic amines (a2-u) preferably have only aromatically bound amino groups, but may also have both (cyclo) aliphatic and aromatic bound reactive amino groups.
• Suitable polyfunctional aromatic amines (a2-u) are, in particular, isomers and derivatives of diaminodiphenylmethane.
• preferred isomers and derivatives of diaminodiphenylmethane are in particular 4,4'- Diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, 2,2'-diaminodiphenylmethane and oligomeric diaminodiphenylmethane.
• Suitable polyfunctional aromatic amines (a2-u) are also in particular isomers and derivatives of toluenediamine.
• preferred isomers and derivatives of toluenediamine are in particular toluene-2,4-diamine and / or toluene-2,6-diamine and diethyltoluenediamines, in particular 3,5-diethyltoluene-2,4-diamine and / or 3.5 diethyltoluene-2,6-diamine.
• component (a2) consists exclusively of polyfunctional aromatic amines of the type (a2-s).
• component (a2) consists of polyfunctional aromatic amines of types (a2-s) and (a2-u).
• component (a2) preferably contains at least one polyfunctional aromatic amine (a2-u) of which at least one is selected from isomers and derivatives of diaminodiphenylmethane (MDA).
• Component (a2) in the second preferred embodiment particularly preferably comprises at least one polyfunctional aromatic amine (a2-u) selected from 4,4'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, 2,2'-diaminodiphenylmethane and oligomeric diaminodiphenylmethane.
• Oligomeric diaminodiphenylmethane contains one or more polynuclear methylene bridged condensation products of aniline and formaldehyde.
• Oligomeric MDA contains at least one, but generally more oligomers of MDA having a functionality of more than 2, in particular 3 or 4 or 5.
• Oligomer MDA is known or can be prepared by methods known per se. Usually, oligomeric MDA is used in the form of mixtures with monomeric MDA.
• the (average) functionality of a polyfunctional amine (a2-u) containing oligomeric MDA can vary in the range of about 2.3 to about 5, more preferably 2.3 to 3.5, and especially 2.3 to 3.
• Such a mixture of MDA-based polyfunctional amines with different functionalities is in particular the crude MDA, which is formed in particular during the condensation of aniline with formaldehyde, usually catalysed by hydrochloric acid, as an intermediate product of the production of crude MDI.
• component (a2) contains oligomeric diaminodiphenylmethane as compound (a2-u) and has an overall functionality of at least 2.1.
• the proportion of the amines of the type (a2-s) according to the general formula I in the total weight of all polyfunctional amines of component (a2), which thus give a total of 100 wt .-%, is preferably from 10 to 100 wt .-%, in particular of 30 to 100 wt .-%, most preferably from 50 to 100 wt .-%, in particular from 80 to 100 wt .-%.
• the proportion of polyfunctional aromatic amines (a2-u) which differ from amines of type (a2-s) in the total weight of all polyfunctional amines of component (a2) is preferably from 0 to 90% by weight, in particular from 0 to 70 wt .-%, particularly preferably from 0 to 50 wt .-%, in particular from 0 to 20 wt .-%.
• the use ratio can vary over a wide range, and in particular from 1.01 to 5. Particularly preferably, said equivalence ratio is from 1.1 to 3, in particular from 1.1 to 2.
• an excess n NC0 over n '''lead s to a lower shrinkage of the porous material, in particular xerogel, in the removal of the solvent and by synergistic interaction with the catalyst to an improved network structure and improved end properties of the resulting porous material.
• the abovementioned components (a1) and (a2) are preferably used in the following ratio, based in each case on the total weight of components (a1) and (a2), which gives 100% by weight: from 20 to 80% by weight .-%, in particular from 25 to 75 Gew. -%, particularly prefers from 35 to 68 Gew. -% of the component (a1), from 20 to 80 Gew. -%, in particular from 25 to 75 Gew preferably from 32 to 65 wt .-% of component (a2).
• the components (a1) and (a2) will hereinafter be referred to collectively as the organic gel precursor (A).
• the process according to the invention is preferably carried out in the presence of at least one catalyst as component.
• Suitable catalysts are, in principle, all catalysts known to those skilled in the art which accelerate the trimerization of isocyanates (so-called trimerization catalysts) and / or the reaction of isocyanates with aromatically bound amino groups (so-called gel catalysts).
• trimerization catalysts the trimerization catalysts
• gel catalysts the reaction of isocyanates with aromatically bound amino groups
• the corresponding catalysts are known per se and have different characteristics with respect to the abovementioned reactions. Depending on their characteristics, they can thus be assigned one or more of the aforementioned types. It is also known to the person skilled in the art that reactions other than those mentioned above may also occur.
• Such catalysts can be characterized, inter alia, by their catalytic activity, e.g. known from polyurethanes, 3rd edition, G. Oertel, Hanser Verlag, Kunststoff, 1993, page 104-1 10.
• Preferred catalysts have a significant trimerization activity. As a result, the homogeneity of the network structure is favorably influenced, resulting in particularly favorable mechanical properties.
• the catalysts may be a monomer (incorporable catalyst) or non-installable, with non-incorporable catalysts are preferred.
• the component is suitably used in the least effective amount.
• Preferred catalysts in component (a4) are selected from the group consisting of primary, secondary and tertiary amines, triazine derivatives, organometallic compounds, metal chelates, quaternary ammonium salts, ammonium hydroxides and alkali metal and alkaline earth metal hydroxides, alkoxides and carboxylates.
• Suitable catalysts are in particular strong bases, for example quaternary ammonium hydroxides, such as. B. tetraalkylammonium hydroxides having 1 to 4 carbon atoms in the alkyl radical and benzyltrimethylammonium hydroxide, alkali metal hydroxides, such as. For example, potassium or sodium hydroxide and alkali metal alkoxides such. For example, sodium methylate, potassium and sodium ethylate and potassium isopropylate. Suitable catalysts are also in particular alkali metal salts of carboxylic acids, such as.
• catalysts are, in particular, N-hydroxyalkyl quaternary ammonium carboxylates, for example trimethylhydroxypropylammonium formate.
• OrganometallENSen are known to those skilled in particular as gel catalysts per se and as catalysts (a4) are also suitable.
• Organotin compounds such as, for example, tin 2-ethylhexanoate and dibutyltin dilaurate are preferred in the context of component (a4).
• Tertiary amines are known per se to the person skilled in the art as gel catalysts and as trimerization catalysts. Tertiary amines are particularly preferred as catalysts (a4). Particularly preferred tertiary amines are ⁇ , ⁇ -dimethylbenzylamine, ⁇ , ⁇ '-dimethylpiperazine, ⁇ , ⁇ -dimethylcyclohexylamine, N, N ', N "-tris (dialkylaminoalkyl) -s-hexahydrotriazines, such as, for example, N, N ', N "-Tris (dimethylaminopropyl) -s-hexahydrotriazine, tris (dimethylaminomethyl) phenol, bis (2-dimethylaminoethyl) ether, ⁇ , ⁇ , ⁇ , ⁇ -pentamethyldiethylenetriamine, methylimidazole, dimethylbenzylamine, 1, 6- Diaz
• catalysts are selected from the group consisting of ⁇ , ⁇ -dimethylcyclohexylamine, bis (2-dimethylaminoethyl) ether, ⁇ , ⁇ , ⁇ , ⁇ , ⁇ -pentamethyldiethylenetriamine, methylimidazole, dimethylbenzylamine, 1, 6 Diazabicyclo-5,4,0-undecene-7, tris (dimethylaminopropyl) -s-hexahydrotriazine, triethylamine, tris (dimethylaminomethyl) phenol, triethylenediamine (diazabicyclo [2,2,2] octane), dimethylaminoethanolamine, dimethylaminopropylamine, N , N-dimethylaminoethoxyethanol, ⁇ , ⁇ , ⁇ -trimethylaminoethylethanolamine, triethanolamine, diethanolamine, triisopropanolamine
• the use of the catalysts preferred in the context of the present invention leads to aerogels and xerogels having smaller mean pore diameters and improved mechanical properties, in particular to improved compressive strength.
• the gelation time is reduced, i. H. accelerates the gelation reaction without negatively affecting other properties.
• the reaction takes place in the presence of a solvent.
• solvent in the context of the present invention comprises liquid
• the mixture may be a true solution, a colloidal solution. solution or a dispersion, for example an emulsion or suspension.
• the mixture is a true solution.
• the solvent is a compound which is liquid under the conditions of step (a), preferably an organic solvent. Suitable solvents are, in principle, an organic compound or a mixture of several compounds, the solvent being liquid at the temperature and pressure conditions under which the mixture is provided in step (a) (in short: solution conditions).
• the composition of the solvent is chosen so that it is able to dissolve or disperse the organic gel precursor, preferably to dissolve.
• Preferred solvents are those which are a solvent for the organic gel precursor (A), ie those which completely dissolve the organic gel precursor (A) under reaction conditions.
• the reaction product of the reaction in the presence of the solvent is first a gel, d. H. a viscoelastic chemical network swollen by the solvent.
• a solvent which is a good swelling agent for the network formed in step (b) usually results in a network of fine pores and small average pore diameter, whereas a solvent which is a poor swelling agent for the gel resulting from step (b) usually results in a coarse-pore network with a large mean pore diameter.
• the choice of solvent thus influences the desired pore size distribution and the desired porosity.
• the choice of the solvent is generally also such that precipitation or flocculation by formation of a precipitated reaction product during or after step (b) of the process according to the invention does not occur as far as possible.
• the proportion of precipitated reaction product is usually less than 1 wt .-%, based on the total weight of the mixture.
• the amount of precipitated product formed in a given solvent can be determined gravimetrically by filtering the reaction mixture before the gel point over a suitable filter.
• Suitable solvents are the solvents known from the prior art for isocyanate-based polymers.
• Preferred solvents are those which are a solvent for the components (a1) and (a2), d. H. those which largely completely dissolve the components of components (a1) and (a2) under reaction conditions.
• the solvent is inert to component (a1), d. H. not reactive.
• suitable solvents are ketones, aldehydes, alkyl alkanoates, amides such as formamide and N-methylpyrollidone, sulfoxides such as dimethyl sulfoxide, aliphatic and cycloaliphatic halogenated hydrocarbons, halogenated aromatic compounds and fluorine-containing ethers. Also suitable are mixtures of two or more of the aforementioned compounds. Furthermore, acetals, in particular diethoxymethane, dimethoxymethane and 1,3-dioxolane, are suitable solvents.
• Dialkyl ethers and cyclic ethers are also suitable as solvents.
• Preferred dialkyl ethers are in particular those having 2 to 6 carbon atoms, in particular methyl ethyl ether, diethyl ether, methyl propyl ether, methyl isopropyl ether, propyl
• Preferred cyclic ethers are in particular tetrahydrofuran, dioxane and tetrahydropyran.
• Aldehydes and / or ketones are preferred as solvents.
• Aldehydes or ketones suitable as solvents are, in particular, those corresponding to the general formula R 2 - (CO) -R 1 , where R 1 and R 2 are hydrogen or alkyl groups having 1, 2 , 3 or 4 carbon atoms.
• Suitable aldehydes or ketones are in particular acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, 2-ethylbutyraldehyde, valaldehyde, isopentaldehyde, 2-methylpentaldehyde, 2-ethylhexaldehydes, acrolein, methacrolein, crotonaldehyde, furfural, acrolein dimer, methacroelindimer, 1, 2,3,6-tetrahydrobenzaldehyde, 6-methyl-3-cyclohexenaldehyde, cyanoacetaldehyde, ethyl glyoxynate, benzaldehyde, acetone, methyl isobutyl ketone, diethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, methyl n
• ketones can also be used in the form of mixtures. Ketones and aldehydes having alkyl groups of up to 3 carbon atoms per substituent are particularly preferred as the solvent. Very particular preference is given to ketones of the general formula R 1 (CO) R 2 , where R 1 and R 2 are selected, independently of one another, from alkyl groups having 1 to 3 C atoms.
• the ketone is acetone.
• at least one of the two substituents R 1 and / or R 2 comprises an alkyl group having at least 2 carbon atoms, in particular methyl ethyl ketone.
• aerogels and xerogels are obtained with a particularly small mean pore diameter.
• the pore structure of the resulting gel is particularly fine-pored due to the higher affinity of the aforementioned particularly preferred ketones.
• particularly suitable solvents result by using two or more completely miscible compounds selected from the aforementioned solvents in the form of a mixture.
• the proportion of components (a1) and (a2) in the total weight of components (a1) and (a2) and the solvent which gives 100% by weight generally not less than 5% by weight.
• the proportion of components (a1) and (a2) in the total weight of components (a1) and (a2) and the solvent which gives 100% by weight is preferably at least 6% by weight, particularly preferably at least 8% by weight. %, in particular at least 10 wt .-%.
• the concentration of the components (a1) and (a2) in the provided mixture must not be set too high, otherwise a porous material having favorable properties will not be obtained.
• the proportion of the components (a1) and (a2) in the total weight of the components (a1) and (a2) and the solvent which gives 100 wt% is at most 40 wt%.
• % in particular at most 20 wt .-%.
• the proportion by weight of components (a1) and (a2) in the total weight of components (a1) and (a2) and of the solvent which gives 100% by weight is in total from 8 to 25% by weight, in particular from 10 to 20 wt .-%, particularly preferably from 12 to 18 wt .-%. Compliance with the amount of starting materials in said range leads to aerogels and xerogels with a particularly favorable pore structure, low thermal conductivity and low shrinkage during drying.
• the method according to the invention comprises at least the following steps:
• step (a) the provision of the components (a1) and (a2) and of the solvent takes place.
• the components (a1) on the one hand and (a2) on the other hand are preferably provided separately from one another in each case in a suitable subset of the solvent.
• the separate provision allows optimal control of the gelation reaction before and during mixing.
• the mixture or mixtures provided in step (a) may also contain conventional auxiliaries known to the person skilled in the art as further constituents. Mention may be made, for example, of surface-active substances, flame retardants, nucleating agents, oxidation stabilizers, lubricants and mold release aids, dyes and pigments, stabilizers, e.g. against hydrolysis, light, heat or discoloration, inorganic and / or organic fillers, reinforcing agents and biocides.
• auxiliaries and additives mentioned above can be found in the specialist literature, e.g. from Plastics Additive Handbook, 5th edition, H. Zweifel, ed. Hanser Publishers, Kunststoff, 2001.
• the catalyst can in principle be added to one of the two components before it is mixed or else after it has been mixed.
• the catalyst is added to the solvent in the presence of component (a2).
• step (b) the reaction of the components (a1) and (a2) in the presence of the solvent to form a gel.
• a homogeneous mixture of the components provided in step (a) must first be generated.
• the mixing of the components provided in step (a) can be carried out in the usual way.
• a stirrer or another mixing device is used to achieve a good and rapid mixing.
• the time required to produce the homogeneous mixture should be small in relation to the time in which the gelation reaction is at least partially formed. a gel to prevent mixing errors.
• the other mixing conditions are generally not critical, for example, you can at 0 to 100 ° C and 0.1 to 10 bar (absolute), especially at room temperature and atmospheric pressure, mix.
• the mixing apparatus is preferably switched off.
• the gelation reaction is a polyaddition reaction, in particular a polyaddition of isocyanate groups and amino groups.
• a gel is to be understood as meaning a crosslinked system based on a polymer which is in contact with a liquid (so-called solvogel or lyogel, or with water as liquid: aquagel or hydrogel).
• the polymer phase forms a continuous spatial network.
• the gel is usually produced by resting, e.g. by simply leaving the container, reaction vessel or reactor in which the mixture is located (hereinafter called gelling device).
• the mixture is no longer stirred or mixed, as this could hinder the formation of the gel. It has proved to be advantageous to cover the mixture during gelling or to close the gelling device.
• the gel obtained in the previous step is dried in step (c).
• drying under supercritical conditions comes into consideration, preferably after replacement of the solvent by CO2 or other solvents suitable for supercritical drying. Such drying is known per se to the person skilled in the art.
• Supercritical conditions indicate a temperature and pressure at which the fluid phase to be removed is in the supercritical state
• the process it is preferable to dry the obtained gels by converting the liquid contained in the gel to the gaseous state at a temperature and a pressure below the critical temperature and the critical pressure of the liquid contained in the gel.
• the drying of the resulting gel is carried out by converting the solvent to the gaseous state at a temperature and a pressure below the critical temperature and the critical pressure of the solvent. Accordingly, drying preferably occurs by removal of the solvent present in the reaction without prior replacement with another solvent.
• Aerogels and Xerogels Properties of the Aerogels and Xerogels and Their Use
• a further subject of the present invention are the aerogels and xerogels obtainable by the process according to the invention.
• Xerogels are preferred as porous materials in the present invention, i. H.
• the porous material obtainable according to the invention is a xerogel.
• a xerogel is understood as meaning a porous material having a porosity of at least 70% by volume and a volume-average mean pore diameter of at most 50 micrometers, which was produced by a sol-gel process, the liquid phase being dried by drying below the critical temperature and below the critical pressure of the liquid phase (“subcritical conditions") was removed from the gel.
• the mean pore diameter is determined by means of mercury intrusion measurement according to DIN 66133 and is in the context of the present invention basically a volume-weighted average.
• the mercury intrusion measurement according to DIN 66133 is a porosimetric method and is carried out in a porosimeter. In this case, mercury is pressed into a sample of the porous material. Small pores require a higher pressure to be filled with mercury than large pores, and from the corresponding pressure / volume plot one can determine a pore size distribution and the volume weighted mean pore diameter.
• the volume-weighted mean pore diameter of the porous material is at most 4 microns.
• the volume-weighted average pore diameter of the porous material is at most 3 micrometers, very particularly preferably at most 2 micrometers and in particular at most 1 micrometer.
• the volume-weighted mean pore diameter is at least 100 nm, preferably at least 150 nm.
• the volume-weighted mean pore diameter is at least 200 nm, in particular at least 300 nm.
• the airgel or xerogel obtainable according to the invention preferably has a porosity of at least 70% by volume, in particular from 70 to 99% by volume, particularly preferably at least 80% by volume, very particularly preferably at least 85% by volume, in particular of 85 to 95% by volume.
• the porosity in% by volume means that said fraction of the total volume of the airgel or xerogel consists of pores.
• the porosity is limited by the mechanical properties and the processability of the airgel or xerogel upwards.
• the components (a1) and (a2) are present in the present invention airgel or xerogel in reacted (polymeric) form.
• the monomer units (a1) and (a2) in the porous material are predominantly bound via urea linkages and / or via isocyanurate linkages, the isocyanurate groups being formed by trimerization of isocyanate groups of the monomer units (a1).
• further possible linkages are, for example, urethane groups, which are formed by reaction of isocyanate groups with alcohols or phenols.
• components (a1) and (a2) in the porous material are at least 50 mol% linked by urea groups -NH-CO-NH- and / or via isocyanurate linkages.
• the components (a1) and (a2) in the porous material are preferably from 50 to 100 mol% linked by urea groups and / or via isocyanurate linkages, in particular from 60 to 100 mol%, very particularly preferably from 70 to 100 mol% , in particular 80 to 100 mol%, for example from 90 to 100 mol%.
• the density of the porous material obtainable according to the invention is usually 20 to 600 g / l, preferably 50 to 500 g / l and particularly preferably 70 to 200 g / l.
• the process of the invention gives a coherent porous material and not just a polymer powder or particles.
• the spatial shape of the resulting porous material is determined by the shape of the gel, which in turn is determined by the shape of the gelling device.
• a cylindrical gelling vessel usually yields an approximately cylindrical gel that can then be dried to a porous, cylindrical material.
• it is also possible to produce a powder for example by grinding the porous material.
• the aerogels and xerogels obtainable according to the invention have a low thermal conductivity, a high porosity and a low density with simultaneously high mechanical stability.
• the porous materials also have a low average pore size.
• the combination of the aforementioned properties allows the use as an insulating material in the field of thermal insulation, in particular for applications in the vacuum sector, where the smallest possible thickness of vacuum plates is preferred, for example in refrigerators or in buildings.
• use in vacuum insulation panels, in particular as a core material for vacuum insulation panels is preferred.
• the use of the aerogels and xerogels of the invention as an insulating material.
• the aerogels and xerogels obtainable according to the invention due to the low thermal conductivity of the aerogels and xerogels obtainable according to the invention, applications are possible at pressures of from 1 to 100 mbar and in particular from 10 mbar to 100 mbar.
• the property profile of the aerogels and xerogels obtainable according to the invention opens up applications in which a long service life of the vacuum panels is desired and even at a pressure increase of about 2 mbar per year after many years, for example at a pressure of 100 mbar, a low Have thermal conductivity.
• the aerogels and xerogels obtainable according to the invention have favorable thermal properties on the one hand and favorable material properties such as ease of processing and high mechanical stability, for example low brittleness, on the other hand.
• Diameter of the porous gel and h is the height of porous gel.
• V s is the specific volume in ml / g of the sample.
• the average pore diameter was determined by means of mercury intrusion measurement according to DIN 66133 and is a volume-weighted mean.
• the lambda value was determined by the dynamic heating wire method.
• a wire is embedded in the sample, which also serves as a heating element and temperature sensor.
• the wire is heated with a constant electrical power. Further details on this measurement method can be found e.g. in H.-P. Ebert et al., High Temp. - High Press., 1993, 25, 391-402. The following compounds were used:
• Oligomeric MDI (Lupranat® M200) with an NCO content of 30.9 g per 100 g according to ASTM D-5155-96 A, a functionality in the range of three and a viscosity of 2100 mPa.s at 25 ° C according to DIN 53018 (hereinafter 'connection M200').
• Oligomeric MDI (Lupranat® M20) with an NCO content of 31, 5 g per 100 g according to ASTM D-5155-96 A, a functionality in the range of three and a viscosity of 210 mPa.s at 25 ° C according to DIN 53018 (hereinafter 'compound M20').
• Component a2 3,3 ', 5,5'-tetraethyl-4,4'-diaminodiphenylmethane (hereinafter "MDEA")
• MDMA 3,3 ', 5,5'-tetramethyl-4,4'-diaminodiphenylmethane
• MDA 4,4'-diaminodiphenylmethane
• the resulting material had a bimodal pore size distribution with pore diameters in the range of 0.4 ⁇ and 2 ⁇ .
• the porosity was 83% by volume with a corresponding density of 185 g / l.
• the material obtained had a bimodal pore size distribution with pore diameters in the range of 0.3 ⁇ and 2 ⁇ .
• the porosity was 83% by volume with a corresponding density of 190 g / l.
• step (a) 1, 6 g of compound M200 were dissolved with stirring at 20 ° C in 10.5 g of acetone in a beaker. 1, 6 g of MDEA were dissolved in 1 1 g of acetone in a second beaker. The two solutions from step (a) were mixed. A clear, low-viscosity mixture was obtained. The mixture was allowed to cure at room temperature for 24 hours. The gel was then removed from the beaker and the liquid (acetone) was removed by drying at 20 ° C for 7 days.
• the material obtained had an average pore diameter of 4 ⁇ .
• the porosity was 89% by volume with a corresponding density of 135 g / l.
• Example V4 1.9 g of compound M200 were dissolved with stirring at 20.degree. C. in 10.5 g of acetone in a beaker. 1.3 g of MDA were dissolved in 11 g of acetone in a second beaker. The two solutions from step (a) were mixed. A clear, low-viscosity mixture was obtained. The mixture was allowed to cure at room temperature for 24 hours. The gel was then removed from the beaker and the liquid (acetone) was removed by drying at 20 ° C for 7 days.
• the material obtained had an average pore diameter of 2.9 ⁇ .
• the porosity was 87% by volume with a corresponding density of 170 g / l.
• Solvent extraction with supercritical C0 2 The gel monolith was transferred to a 250 ml autoclave.
• the autoclave was filled with> 99% acetone so that the gel monolith was completely covered by acetone and then sealed.
• the monolith was dried in C0 2 stream for 24 hours.
• the pressure (in the drying system) was between 1 15 and 120 bar; the temperature was 40 ° C. At the end, the pressure in the system was controlled to reduce to atmospheric pressure within about 45 minutes at a temperature of 40 ° C.
• the autoclave was opened and the resulting porous material was taken out.
• the resulting porous material had a density of 136 g / l.
• the lambda value was 19.8 mW / m * K (pressure 1 bar).

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